This ongoing program has assembled for study all known and suspected epidemiologic and genetic events, attributes and factors possibly related to risk of prostatic carcinoma, searching for those which may directly or indirectly influence onset of the lesion. Objectives are to explore strategies for prevention and early detection of this prevalent cancer, to identify individuals at increased risk, to provide hypotheses useful in repeat studies and prospective designs, to establish a rationale for the development of prostatic cancer and to structure models for oncogenesis in the human prostate, to develop an information base for screening programs, and to reduce morbidity and mortality rates from this disease in the population. The research design is a collaborative retrospective matched-pair case-control study, and sampling has taken place at 3 major institutions in 2 widely separated metropolitan areas, Chicago and Los Angeles, providing multiple-hospital access to large populations of prostatic cancer patients, opportunity for reproducibility comparisons by institutions, by geography, by race and by socioeconomic level; and also full studies of 500 securely diagnosed patients against 500 controls without clinically diagnosable cancer of any site and of benign prostatic hypertrophy. Epidemiologic and genetic information was obtained with interviewer administered questionnaires and related instruments inquiring into behavioral, sociocultural, sexual, physical, psychological and clinical associates with risk of the carcinoma. Familial studies are conducted into 3 generations of each kinship, with patients and controls as probands. Cases and controls have been sampled and preliminary results have been reported. We now are preparing to process matching samples of benign hypertrophy patients, and concurrently to move into the analysis phase of the study, including genetic followup, full sample data processing and treatments, end results, assessment of trends, interpretations and reports.